UK is considering chemical castration for sex offenders. What is it?

The British government is planning to start using chemical castration to reduce the sex drive of offenders.

Justice Secretary Shabana Mahmood said the treatment will be introduced in 20 prisons across two regions. She also mentioned she is thinking about making it compulsory.

The treatment is expected to lower the offender’s sex drive and reduce sexual thoughts.

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It is worth noting that chemical castration has already been used in countries like Germany and Denmark. In the UK , too, it has been used before, but only for men who chose the treatment.

So, what exactly is chemical castration? Why is the UK bringing it in now? How does it work? This explainer will look at these questions.

Let’s find out:

What is chemical castration?

Chemical castration involves using medicines to block the production of sex hormones in the body.

Hormones are released by different glands and travel through the bloodstream, sending signals to various parts of the body. They help control things like energy levels, growth, and mood.

Sex hormones in particular trigger puberty and support the body’s reproductive functions, according to the Cleveland Clinic.

This treatment is given through medication, along with psychiatric support. It is mainly used for sex offenders who have ongoing, obsessive thoughts about sex or show troubling sexual behaviour.

How will it work in the UK? Why is it being introduced?

The UK plans to begin using medication to lower the sex drive of certain sex offenders.

This move is part of a wider effort to reduce reoffending and ease pressure on the prison system, which is close to full capacity.

Justice Secretary Shabana Mahmood said in Parliament, following the release of an independent sentencing review, “Of course, it is vital that this approach is taken alongside psychological interventions that target other causes of offending, like asserting power and control.”

While the review pointed out that the treatment may not suit all sex offenders, such as those whose actions are linked to control and violence rather than sexual urges, Mahmood noted that research suggests chemical castration can reduce reoffending by as much as 60 per cent.

The suggestion came from a major review led by former Justice Secretary David Gauke. The review not only looked at ways to cut reoffending but also recommended major changes to a prison system nearing its limits.

One of Mahmood’s early decisions as justice minister, after Labour returned to power last July following 14 years in opposition, was to approve an early-release scheme to create space in prisons.

She said she had inherited a justice system that had long been overlooked under the previous Conservative government and launched the review to bring stability back.

Mahmood is now considering whether the chemical castration programme should be made available across the country, and whether it should become compulsory. There is currently no set timeline for this decision.

So far, the government has not confirmed which areas or prisons will be involved in the expanded pilot.

Gauke’s report noted that, as of the end of March 2025, sexual offences made up 21 per cent of adult prison sentences being served.

The review recommended creating a strong evidence base for the use of chemical castration and suggested looking into continued funding for these services, according to BBC.

However, it also warned that this form of treatment “should never be used as a risk management tool or standalone rehabilitative offer, and it is only appropriate for a limited number of sex offenders”.

However, Shadow Justice Secretary Robert Jenrick raised concerns, saying mandatory chemical castration could breach human rights laws. He claimed the government was using the policy as a distraction.

“This is a dead cat story from a Labour Government desperate to distract from its dangerous plan to let arsonists, paedophiles and child abusers get away with serving just a fifth of their sentence,” he was quoted as saying by The Telegraph UK.

The sentencing changes aim to free up 9,800 prison spaces, a 10 per cent reduction, by 2028, to help manage the overcrowding crisis and stop jails from running out of room.

Who will be part of this?

As part of the new plans, the system allowing automatic release after serving 40 per cent, 50 per cent or two-thirds of a sentence, based on the 1991 Criminal Justice Act, will be removed.

According to The Telegraph UK, serious offenders such as killers, rapists, and others convicted of violent or sexual crimes will now be released halfway through their sentence instead of two-thirds, but only if they follow prison rules and take part in rehabilitation programmes.

This change will apply to thousands of prisoners who are serving “determinate” or fixed-term sentences of four years or more. These include crimes like rape, manslaughter, attempted murder, soliciting murder, and causing grievous bodily harm with intent.

Meanwhile, people convicted of less serious crimes, such as burglary, theft, fraud and assault, could be released after serving just a third of their sentence, provided they maintain good behaviour, the report added.

Under an “earned progression” system, these offenders may spend up to one-third of their remaining sentence on an “enhanced” licence. During this time, they could be monitored through electronic tags, subject to curfews, and may even have their passports taken away.

The final third of the sentence would be served on a standard licence, where breaking the rules could mean being sent back to prison.

How effective is chemical castration?

Chemical castration involves the use of two types of medication. Selective serotonin reuptake inhibitors (SSRIs) help reduce intrusive sexual thoughts, while anti-androgens lower testosterone levels and decrease sex drive.

These drugs are used along with psychiatric support to address deeper reasons behind sexual offending, such as a desire to assert control or power.

Though research is still limited, early findings show a drop in reoffending rates. According to BBC, one study tracked ten offenders after treatment, none of them committed another offence.

In another study, two groups were compared: one group received chemical castration while the other did not. The reoffending rate was found to be 60 per cent lower in the group that received the treatment.

With inputs from agencies